One known type of information storage device is disk drive device. In data reading/writing operation, a disk with a magnetic layer in the disk drive rotates at a high speed such that an air bearing is generated between the disk and the slider disposed above the disk; therefore, the slider is dynamically floated above the disk and a certain flying height for the slider is maintained. The data information is written to or read from the magnetic layer via a magnetic read/write element incorporated in the slider.
Presently, this type of hard disk drives (HDDs) are booming with digital devices, such as digital cameras and audio/video devices and even television sets, which require a large amount of storage. Thus, there is a huge market demand for the HDDs, especially for the HDD with high areal density and small physical volume.
High areal density of recording can be accomplished by, either improving magnetic performance of the magnetic coating on the disk surface or reducing the size of the magnetic read/write slider that access data stored in the magnetic coating. Size reduction of the read/write slider results in a weaker read/write signal; accordingly, the magnetic track width and/or the magnetic track pitch are also decreased. However, the key aspects of decreasing the magnetic track width and/or track pitch are to improve the position control of the read/write slider, such as the flying height control, which represents the distance between the disk surface and the read/write slider when the slider is flying above the disk surface. In addition, controls for slider pole tip recession and thickness of protective coating for both the magnetic slider and the disk surface are also key points for achieving the above object.
On the other hand, minimizing the physical volume of the HDD is a systematic engineering, which concerns not only changes in the component physical dimension of the HDD, but also re-optimization of flying dynamics performance of the slider. Currently, the size of HDD for desktop computer is 3.5 inches, and the size of HDD for notebook computer is 2.5 inch. For applications in portable digital audio/video device, the size of the HDDs is down to 1 inch or even 0.85 inch.
As is known to all, slider is an important component of the HDD. FIG. 1a shows a typical slider used in HDD, which is viewed from ABS (a surface of the slider facing to a disk) of the slider. As illustrated, the slider 10 comprises an ABS 18, a leading edge 15 and a trailing edge 13 opposite to the leading edge 15. A pole tip 11 is provided on the trailing edge 13, the pole tip 11 has read/write elements for achieving data read/write operation. A shallow etched area 12 is provided adjacent to the leading edge 15 for controlling airflow entering into the ABS.
FIG. 1b shows an enlarged view of the pole tip of FIG. 1a, and FIG. 1c shows a partial, sectional view of the pole tip shown in FIG. 1a along A-A line thereof. As illustrated, the pole tip 11 has a laminated structure, which comprises from top to bottom a first shielding layer 113, a second shielding layer 111, a first inductive write head pole 118 and a second inductive write head pole 116 spacing away from the first inductive write head pole 118. All above components are carried on a substrate 122 of the slider. A magneto-resistive element 112 and a lead layer 114 disposed at two sides of the magneto-resistive element 112 and electrically connected to the magneto-resistive element 112 are provided between the second shielding layer 111 and the first shielding layer 113. A coil 117 is positioned between the first inductive write head pole 118 and second inductive write head pole 116 for realizing writing operation.
The slider has a very flat surface in its pole tip region. The surface is formed usually by lapping the substrate of the slider. The very flat surface of the slider has a roughness (Ra) of less than 0.3 nm. The lapping process may also provide assistance in controlling pole tip recess.
For small-sized HDD, which is often referred to as a micro disk drive, its slider substrate is required to have a very high surface roughness, namely, it is necessary to form micro-texture on a surface (ABS) of the slider for improving take-off and touch-down performance thereof. Since the rougher the slider substrate is, the more notable the microcosmic concave and convex structure of the slider surface topography is. This means more air will be contained in the concave-convex structure, therefore, when the slider takes off from or touches down to the disk surface, physical friction of the slider and/or disk surface will be reduced, and thus decreasing abrasion of the slider and/or disk, accordingly greatly lengthening life-span of the slider and/or disk. The micro-texture is conventionally formed on ABS of the slider by etching substrate of the slider using etching means. The slider substrate is generally made of AlTiC, which is a mixture of alumina (Al2O3) and titanium carbide (TiC). In etching process, as Al2O3 is etched more rapidly than TiC, so island-like TiC grains embedded in Al2O3 base body will be formed on the ABS. FIGS. 2a-2b illustrate this so-formed microstructure due to difference in etching speed. FIG. 2a illustrates a phase image of the microstructure, in which white region designated by numeral 120 represents extruded island-like TiC grains, while black region designated by numeral 119 represents Al2O3 base body. FIG. 2b shows a cross-sectional view of the microstructure. As illustrated, it is the interlaced island-like TiC grains 120 and Al2O3 base body 119 to form the micro-texture of the ABS.
Conventional etching method for forming micro-texture on ABS of the slider generally uses a pure gas such as Argon, or oxygen (O2), or a mixture gas of Argon and oxygen as its processing gas during etching process. By ionizing the processing gas to generate ion beams of high energy for continuously bombarding the slider surface so as to make atoms on the slider surface escape therefrom, i.e. an etching action happens on the slider surface. The ion bombarding is also referred as to ion beam milling. During etching process, almost no chemical reaction happens between the ion beams and material of the slider surface, but only momentum transfer happens. Though this conventional etching means is able to form micro-texture on ABS of the slider, it is very difficult for thus formed micro-texture to obtain a roughness that meets the demand of micro-disk drives, because this ion etching is mainly a physical reaction, and in this physical etching process, the above ionized processing gas (Argon or oxygen) renders little speed difference in etching Al2O3 and TiC. That is, etching ratio of Al2O3/TiC is very smaller. The etching ratio keeps very small and cannot meet the requirement even when an etching process is performed by ion beam with a glancing incidence angle.
In case where high etching ratio cannot be obtained by conventional etching method, to obtain a rougher micro-texture, a method commonly used in the field is by increasing etching volume. That is, the height difference between the Al2O3 base body and the island-like TiC grains are increased by extending etching time. FIGS. 4a-4b show the etching process. FIG. 4a shows a slider substrate 122 after it is lapped but before it is etched, in which lapped slider surface 123 is taken as a datum surface for measuring etching height, and distance between the pole tip 11 and the datum surface 123 is d1. FIG. 4b shows a state after the slider substrate is etched, in which numeral 124 represents micro-texture formed by etching process, d2 represents distance between the etched pole tip 11 and the datum surface 123, a difference between d1 and d2 represents etched height of the pole tip, while D1 represents etched height of the slider substrate beyond the pole tip. It is obtained from measurement that difference between d1 and d2 is larger than D1; that is, the pole tip is etched by the ion beams more seriously than other region.
The big volume of etching has bad influences on the pole tip. Firstly, big volume of etching may readily cause damage to the pole tip, especially damage to magnetic domain of the pole tip, thus effecting electromagnetic characteristic of the slider; secondly, the pole tip is made of many kinds of materials such as materials for constructing the inductive write head pole, shielding layers, magneto-resistive (MR) element, leads and hard magnetic bias. These materials have different etching rates due to different material nature of themselves. Big volume of etching in the pole tip region produces an undulated surface, therefore, not only original topography of the pole tip is destructed, but also performance of the slider is degraded to some extent. In addition, reliability of the diamond-like carbon layer (DLC) formed on the surface of the pole tip in latter process is decreased, or instead, a thickness of the DLC layer must be increased for deleting the influence of surface unevenness; however, increment in thickness of the DLC layer will make a distance between the MR sensor and the magnetic layer of the disk increased, and this will weaken read/write signals of the slider.
Thus, there is a need for an improved method that does not suffer from the above-mentioned drawbacks.